Biology subjects

Varshney, R.

Publications and source records attributed to Varshney, R..

9 recordsLinked to original sources

bioRxiv2025

Lipodystrophy and recovery are mediated by the Wnt/lipogenesis axis during skin fibrosis.

Acquired lipodystrophy in the dermal white adipose tissue (DWAT) is a salient feature of skin fibrosis, and is followed by accumulation of extracellular matrix (ECM). Lipodystrophy syndromes, often associated with metabolic co-morbidities, are estimated to affect 1 in 20,000 people. We recently showed that fibrosis-associated lipodystrophy is dependent on sustained Wnt signaling, but the mechanism is unclear. Transcriptomic profiling of mature dermal adipocytes in vivo reveal that Wnt activation downregulates the de novo-lipogenesis (DNL) axis enzymes within 48 hours. We found that protein expression of Fatty Acid Synthase (FASN), a key DNL enzyme, is dependent on sustained Wnt activation in vitro and in vivo. In human systemic sclerosis, FASN mRNA is significantly downregulated during two years of disease. Remarkably, pharmacological inhibition of FASN enzyme during reversal from Wnt induced fibrosis impedes recovery of DWAT lipid content as well as ECM accumulation and topography. All together, we demonstrate that acquired lipodystrophy in the context of skin fibrosis is mediated by a new role of the Wnt-DNL axis. These findings underscore the importance of this pathway in lipodystrophy and fibrosis, opening new avenues for therapeutic targets in skin fibrosis.

cell biology↗

bioRxiv2024

NR2F2 Reactivation in Early-life Adipocyte Stem-like Cells Rescues Adipocyte Mitochondrial Oxidation

In humans, perinatal exposure to an elevated omega-6 (n6) relative to omega-3 (n3) Fatty Acid (FA) ratio is associated with the likelihood of childhood obesity. In mice, we show perinatal exposure to excessive n6-FA programs neonatal Adipocyte Stem-like cells (ASCs) to differentiate into adipocytes with lower mitochondrial nutrient oxidation and a propensity for nutrient storage. Omega-6 FA exposure reduced fatty acid oxidation (FAO) capacity, coinciding with impaired induction of beige adipocyte regulatory factors PPAR{gamma}, PGC1, PRDM16, and UCP1. ASCs from n6-FA exposed pups formed adipocytes with increased lipogenic genes in vitro, consistent with an in vivo accelerated adipocyte hypertrophy, greater triacylglyceride accumulation, and increased % body fat. Conversely, n6-FA exposed pups had impaired whole animal 13C-palmitate oxidation. The metabolic nuclear receptor, NR2F2, was suppressed in ASCs by excess n6-FA intake preceding adipogenesis. ASC deletion of NR2F2, prior to adipogenesis, mimicked the reduced FAO capacity observed in ASCs from n6-FA exposed pups, suggesting that NR2F2 is required in ASCs for robust beige regulator expression and downstream nutrient oxidation in adipocytes. Transiently re-activating NR2F2 with ligand prior to differentiation in ASCs from n6-FA exposed pups, restored their FAO capacity as adipocytes by increasing the PPAR{gamma}-PGC1 axis, mitochondrial FA transporter CPT1A, ATP5 family synthases, and NDUF family Complex I proteins. Our findings suggest that excessive n6-FA exposure early in life dampens an NR2F2-mediated induction of beige adipocyte regulators, resulting in metabolic programming that is shifted towards nutrient storage.

physiology↗

bioRxiv2024

Non-Necroptotic Roles of MLKL in Diet-Induced Obesity, Liver Pathology, and Insulin Sensitivity: Insights from a High Fat, High Fructose, High Cholesterol Diet Mouse Model

Chronic inflammation is a key player in metabolic dysfunction-associated fatty liver disease (MAFLD) progression. Necroptosis, an inflammatory cell death pathway, is elevated in MAFLD patients and mouse models, yet its role is unclear due to diverse mouse models and inhibition strategies. In our study, we inhibited necroptosis by targeting mixed lineage kinase domain like pseudokinase (MLKL), the terminal effector of necroptosis, in a high-fat, high-fructose, high-cholesterol (HFHFrHC) mouse model of diet-induced MAFLD mouse model. Despite HFHFrHC diet upregulating MLKL (2.5-fold), WT mice livers showed no increase in necroptosis markers or associated proinflammatory cytokines. Surprisingly, Mlkl-/-mice experienced exacerbated liver inflammation without protection from diet-induced liver damage, steatosis, or fibrosis. In contrast, Mlkl+/- mice showed significant reduction in these parameters that was associated with elevated Ppar and Ppar{gamma} levels. Both Mlkl-/-and Mlkl+/- mice on HFHFrHC diet resisted diet-induced obesity, attributed to increased beiging, enhanced oxygen consumption and energy expenditure due to adipose tissue, and exhibited improved insulin sensitivity. These findings highlight the tissue specific effects of MLKL on the liver and adipose tissue, and suggest a dose-dependent effect of MLKL on liver pathology.

biochemistry↗

bioRxiv2023

DNA Tetrahedral Nanocages as a Promising Nanocarrier for Dopamine Delivery in Neurological Disorders

Dopamine is a neurotransmitter in the central nervous system that is essential for many bodily and mental processes, and a lack of it can cause Parkinsons disease. DNA tetrahedral (TD) nanocages are promising in bio-nanotechnology, especially as a nanocarrier. TD is highly programmable, biocompatible, and capable of cell differentiation and proliferation. It also has tissue and blood-brain barrier permeability, making it a powerful tool that could overcome potential barriers in treating neurological disorders. In this study, we used DNA-TD as a carrier for Dopamine to cells and zebrafish embryos. We investigated the mechanism of complexation between TD and dopamine hydrochloride using gel electrophoresis, fluorescence and circular dichroism (CD) spectroscopy, atomic force microscopy (AFM), and molecular dynamic (MD) simulation tools. Further, we demonstrate these Dopamine-loaded DNA tetrahedral nanostructures cellular uptake and differentiation ability in SH-SY5Y neuroblastoma cells. Furthermore, we extended the study to zebrafish embryos as a model organism to examine survival and uptake. The research provides valuable insights into the complexation mechanism and cellular uptake of dopamine-loaded DNA tetrahedral nanostructures, paving the way for further advancements in nanomedicine for Parkinsons disease and other neurological disorders.

bioengineering↗

bioRxiv2023

Dopamine functionalized, red carbon quantum dots for in vivo bioimaging, cancer therapeutics, and neuronal differentiation

One of the crucial requirements of quantum dots for biological applications is their surface modifications for very specific and enhanced biological recognition and uptake. Toward this, we present the green synthesis of bright, red-emitting carbon quantum dots derived from mango leaf extract (mQDs). These mQDs are conjugated electrostatically with dopamine to form mQDs-dopamine (mQDs: DOPA) bioconjugates. Bright red fluorescence of mQDs was used for bioimaging and uptake in multiple cell lines, tissues, and in vivo models like zebrafish. mQDs exhibited the highest uptake in brain tissue as compared to others. mQD:DOPA conjugate induced cellular toxicity only in cancer cells while showing increased uptake in epithelial cells and zebrafish. Additionally, the mQDs: DOPA promoted neuronal differentiation of SH-SY5Y cells to complete neurons. Both mQDs and mQDs: DOPA exhibited potential for higher collective cell migrations implicating their future potential as next-generation tools for advanced biological and biomedical applications. TOCmQDs were electrostatically conjugated with dopamine (DOPA) to form the mQDs: DOPA bioconjugate. mQDs are used to image cells, tissues, and zebrafish embryos. mQDs: DOPA kills cancer cells, differentiates neuronal cells, and increases the uptake of mQDs in zebrafish embryos. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=116 SRC="FIGDIR/small/545347v1_ufig1.gif" ALT="Figure 1"> View larger version (25K): org.highwire.dtl.DTLVardef@f521a4org.highwire.dtl.DTLVardef@173a8f0org.highwire.dtl.DTLVardef@585271org.highwire.dtl.DTLVardef@8c959d_HPS_FORMAT_FIGEXP M_FIG C_FIG

bioengineering↗

bioRxiv2023

PROX1 inhibits PDGF-B expression to prevent myxomatous degeneration of heart valves

BackgroundCardiac valve disease (CVD) is observed in 2.5% of the general population and 10% of the elderly people. Effective pharmacological treatments are currently not available, and patients with severe CVD require surgery. PROX1 and FOXC2 are transcription factors that are required for the development of lymphatic and venous valves. We found that PROX1 and FOXC2 are expressed in a subset of valvular endothelial cells (VECs) that are located on the downstream (fibrosa) side of cardiac valves. Whether PROX1 and FOXC2 regulate cardiac valve development and disease is not known. MethodsWe used histology, electron microscopy and echocardiography to investigate the structure and functioning of heart valves from Prox1{Delta}VEC mice in which Prox1 was conditionally deleted from VECs. Isolated valve endothelial cells and valve interstitial cells were used to identify the molecular mechanisms in vitro, which were tested in vivo by RNAScope, additional mouse models and pharmacological approaches. The significance of our findings was tested by evaluation of human samples of mitral valve prolapse (MVP) and aortic valve insufficiency. ResultsHistological analysis revealed that the aortic and mitral valves of Prox1{Delta}VEC mice become progressively thick and myxomatous. Echocardiography revealed that the aortic valves of Prox1{Delta}VEC mice are stenotic. FOXC2 was downregulated and platelet-derived growth factor-B (PDGF-B) was upregulated in the VECs of Prox1{Delta}VEC mice. Conditional knockdown of FOXC2 and conditional overexpression of PDGF-B in VECs recapitulated the phenotype of Prox1{Delta}VEC mice. PDGF-B was also increased in mice lacking FOXC2 and in human MVP and insufficient aortic valve samples. Pharmacological inhibition of PDGF-B signaling with imatinib partially ameliorated the valve defects of Prox1{Delta}VEC mice. ConclusionPROX1 antagonizes PDGF-B signaling partially via FOXC2 to maintain the extracellular matrix composition and prevent myxomatous degeneration of cardiac valves. Novelty and SignificanceWhat Is Known? O_LIThe transcription factors PROX1 and FOXC2 are critical regulators of lymphatic and venous valve development. C_LIO_LIPROX1 and FOXC2 are expressed in the downstream valvular endothelial cells of heart valves. C_LI What Is New? O_LIDeletion of Prox1 from the valvular endothelial cells of mice results in enlarged and myxomatous aortic and mitral valves. Aortic valves of the mutant (Prox1{Delta}VEC) mice were stenotic. C_LIO_LIFOXC2 is partially responsible for the phenotype of Prox1{Delta}VEC mice. C_LIO_LIPROX1 and FOXC2 inhibit the expression of the cytokine PDGF-B in heart valves. C_LIO_LIHyperactivation of PDGF-B signaling results in aortic and mitral valve thickening. C_LIO_LIInhibition of PDGF-B signaling ameliorates aortic valve stenosis in Prox1{Delta}VEC mice. C_LIO_LIPDGFB is overexpressed and PROX1 is downregulated in human mitral valve prolapse (MVP) samples. C_LI Our findings suggest that PROX1 is an inhibitor of myxomatous valve disease that afflicts ~10% of the elderly population. We have also identified PDGF-B as a potential target for treating myxomatous valve disease.

developmental biology↗

bioRxiv2022

Hypothalamic melanocortin-4 receptors on astrocytes mediate inflammation and body weight homeostasis

World-wide, nearly 40% of the adult population is classified as clinically obese. Central inflammation is highly correlated with obesity and increases morbidity and deterioration of health. The hypothalamus is a brain region that governs many facets of energy homeostasis, and melanocortins in the hypothalamus both decrease feeding and increase metabolism via melanocortin-4 receptors (MC4Rs). Although MC4Rs are present on neurons and astrocytes (aMC4R) previous work has focused almost exclusively on the neuronal population with the contribution of aMC4R on these processes largely unknown. Our objective was to determine the effects of hypothalamic aMC4R deletion on central and peripheral inflammation, as well as feeding and body weight homeostasis. Adult MC4R fl/fl mice were microinjected with an astrocyte-specific promoter driving Cre-expression (AAV-GFAP-GFP-Cre) or AAV-control (AAV-GFAP-GFP; n=4-7/group/sex) to produce a hypothalamic knock-down of aMC4R (KD). Body weight and composition were monitored throughout the study, and indirect calorimetry was conducted at 1 and 4 weeks after AAV injection. Acquisition of operant self-administration of palatable food was also examined. Mice were euthanized 7-8 weeks post AAV injection and brain and tissue samples were collected. We observed a significant increase in body weight, feeding, and energy balance in the KD group compared to control group. Inflammation was significantly increased centrally in KD mice within the hypothalamus, but not peripherally within serum. Additionally, aMC4R KD mice trended towards an increased reward learning for palatable food. This is the first demonstration that hypothalamic aMC4R, independent of neuronal MC4R, is important in modulating inflammation as well as contributing to energy balance. These results provide an integral understanding of the aMC4R system that will provide the foundation for future studies investigating the role of aMC4R in various disease states.

neuroscience↗

bioRxiv2020

Performance of Bracon brevicornis (Wesmael) on two Spodoptera species and application as potential biocontrol agent against fall armyworm

Successful pest management using parasitoids requires careful evaluation of host-parasitoid interactions. Here, we report the performance of larval ecto-parasitoid wasp, Bracon brevicornis (Wesmael) on important agricultural pests, Spodoptera litura (Fabricius) and S. frugiperda (J.E. Smith). Biology of B. brevicornis was studied on different host instars under laboratory and cage setup. In no-choice assay, the parasitoid development was highest on fifth instar S. litura larvae as the wasp laid ∼253 eggs with 62% hatching, 76% pupae formation and 78% adult emergence. Similarly, these parameters were highest on fifth instar S. frugiperda larvae (293 eggs, 57% hatching, 80% pupae formation, 70% adult emergence). In two-choice assay, B. brevicornis preferred fourth or fifth over third instar larvae of both hosts. Successful parasitism depends on host paralysis and suppression of host immunity. B. brevicornis interaction downregulated cellular immunity of both hosts as shown by reduced hemocyte viability and spreading. The percent parasitism rate of B. brevicornis was unaltered in the presence of host plant, Zea mays in cage study. 76 and 84% parasitism was observed on fifth instar larvae of S. litura and S. frugiperda, respectively. We evaluated the performance of B. brevicornis as a biocontrol agent on S. frugiperda in maize field. Our results show 54% average reduction in infestation after release of B. brevicornis. Taken together, we report the performance of B. brevicornis on important insect pests for the first time in laboratory and field conditions. Our findings indicate that B. brevicornis is a promising candidate for integrated pest management.Key messagesWe have evaluated the instar preference and performance of B. brevicornis as a potential biocontrol agent for two serious pests, Spodoptera litura and S. frugiperda.Fifth instar larva was most suitable for B. brevicornis development irrespective of the host species. B. brevicornis attack induced permanent paralysis and down-regulated cellular immunity of both hosts.Our field experiment confirmed B. brevicornis as a promising parasitoid for controlling S. frugiperda, a highly invasive pest of growing concern.Competing Interest StatementThe authors have declared no competing interest.View Full Text

ecology↗

bioRxiv2019

Carbohydrate, glutathione, and polyamine metabolism are central to Aspergillus flavus oxidative stress responses over time

The primary and secondary metabolites of fungi are critical for adaptation to environmental stresses, host pathogenicity, competition with other microbes, and reproductive fitness. Drought-derived reactive oxygen species (ROS) have been shown to stimulate aflatoxin production and regulate development in Aspergillus flavus, and may function in signaling with host plants. Here, we have performed global, untargeted metabolomics to better understand the role of aflatoxin production in oxidative stress responses, and also explore isolate-specific oxidative stress responses over time. Two field isolates of A. flavus, AF13 and NRRL3357, possessing high and moderate aflatoxin production, respectively, were cultured in medium with and without supplementation with 15mM H2O2, and mycelia were collected following 4 and 7 days in culture for global metabolomics. Overall, 389 compounds were described in the analysis which were examined for differential accumulation. Significant differences were observed in both isolates in response to oxidative stress and when comparing sampling time points. The moderate aflatoxin-producing isolate, NRRL3357, showed extensive stimulation of antioxidant mechanisms and pathways including polyamines metabolism, glutathione metabolism, TCA cycle, and lipid metabolism while the highly aflatoxigenic isolate, AF13, showed a less vigorous response to stress. Carbohydrate pathway levels also imply that carbohydrate repression and starvation may influence metabolite accumulation at the later timepoint. Higher conidial oxidative stress tolerance and antioxidant capacity in AF13 compared to NRRL3357, inferred from their metabolomic profiles and growth curves over time, may be connected to aflatoxin production capability and aflatoxin-related antioxidant accumulation. The coincidence of several of the detected metabolites in H2O2-stressed A. flavus and drought-stressed hosts suggests their potential role in the interaction between these organisms and their use as markers/targets to enhance host resistance through biomarker selection or genetic engineering.\n\nAuthor SummaryAspergillus flavus is a fungal pathogen of several important crops including maize and peanut. This pathogen produces carcinogenic mycotoxins known as aflatoxins during infection of plant materials, and is particularly severe under drought stress conditions. This results in significant losses in crop value and poses a threat to food safety and security globally. To combat this, understanding how this fungus responds to environmental stresses related to drought can allow us to identify novel methods of mitigating aflatoxin contamination. Here, we analyzed the accumulation of a broad series of metabolites over time in two isolates of A. flavus with differing stress tolerance and aflatoxin production capabilities in response to drought-related oxidative stress. We identified several metabolites and mechanisms in A. flavus which allow it to cope with environmental oxidative stress and may influence aflatoxin production and fungal growth. These may serve as potential targets for selection in breeding programs for the development of new cultivars, or for alteration using genetic engineering approaches to mitigate excessive aflatoxin contamination under drought stress.

microbiology↗